A new test may help detect cancers of the ovaries and the endometrium. / Keith Brofsky, Getty Images

by Liz Szabo, USA TODAY

by Liz Szabo, USA TODAY

The Pap smear, first developed in the 1940s, is often described as the world's most successful cancer screening test. Deaths from cervical cancer, once a major killer of American women, have fallen 75% since the Pap smear's introduction.

Now, doctors are combining this grandfather of all screening tests with the latest genomic research in an effort to detect cancer of the ovaries and the endometrium, or uterine lining.

In a surprise finding, researchers discovered that cervical fluid, obtained during a Pap smear, may contain not only cells from cervical cancer, but from ovarian or endometrial cancer, as well.

Using sophisticated new methods of sequencing DNA, doctors scanned this fluid for genetic mutations found only in ovarian or endometrial cancers, according to a pilot study published online Wednesday in Science Translational Medicine.

Authors note that their study was small, with samples from just 24 endometrial cancers and 22 ovarian cancers.

The research is in its earliest stages, and is nowhere close to being ready to be used in the clinic, says co-author Nickolas Papadopoulos, a professor of oncology at Johns Hopkins Kimmel Cancer Center. He plans to conduct additional studies with hundreds of tumor samples.

But the test, called PapGene, appears promising, he says. It found 100% of the endometrial cancers and 41% of ovarian cancers.

Developing an early screening test for a disease as deadly as ovarian cancer is akin to finding "the Holy Grail," says Shannon Westin, of Houston's M.D. Anderson Cancer Center, who wrote an accompanying editorial.

That's because ovarian cancers are typically found very late, when they are incurable, Westin says.

Finding ovarian cancers earlier could help a lot of women, Westin says. Five-year survival rates for early ovarian cancers, which haven't spread, are 92%. Overall ovarian cancer survival rates, however, are only 44%.

In contrast, endometrial cancers are often diagnosed early, due to symptoms such as vaginal bleeding, Westin says. Five-year survival rates for uterine cancer are 83%.

So far, the ovarian cancer part of the test isn't sensitive enough to recommend to the general public, Westin says. In comparison, Pap smears catch nearly all cervical cancers and most precancers, she says.

Authors hope to refine the test to make it more accurate.

Yet experts call the screening test exciting, if only because it looks for cancer in a completely new way.

Maurie Markman, a spokesman for the American Society of Clinical Oncology, called the approach "fascinating."

"It opens up a lot of research opportunities," says Markman, senior vice president of clinical affairs at Cancer Treatment Centers of America. "This should definitely be pursued."

Scientists have been searching for "biomarkers" of cancer for years, hoping to find a protein or other signal that could help detect cancer through a blood test. And in spite of promising early results, researchers also have produced "hundreds of examples of false leads" that could never be replicated, Markman says.

Still, researchers are making progress, says the National Cancer Institute's Sudhir Srivastava. Five cancer biomarker tests have received Food and Drug Administration approval.

The PapGene approach is also intriguing, he says, because it could be combined with screenings that women already undergo. That could help to reduce the cost.

And while genomic tests are still expensive, the cost is falling every day, thanks partly due to more powerful computers and more sophisticated software, Westin says.

The study was funded by a variety of sources, including the National Institutes of Health and private charities.

Papadopoulos and several of his co-authors are co-founders of Inostics and Personal Genome Diagnostics, which has licensed some of the technical aspects involved in PapGene tests to other companies.

About 15,500 American women die of ovarian cancer each year, along with more than 8,000 who die of uterine cancer, according to the American Cancer Society.

Endometrial cancer is one of only a handful of cancers that are increasing in both incidence rates and deaths, according to a report released this week from the cancer society and other groups. Researchers believe rising rates of obesity, which increases the risk of endometrial cancer, are fueling the trend.